Natural killer cell defects resulting from thermal injury

Increased serum NKG2D-ligands and downregulation of NKG2D in peripheral blood NK cells of patients with major burns

Immune suppression following major thermal injury directly impacts the recovery potential. Limited data from past reports indicate that natural killer cells might be suppressed due to a putative soluble factor that has remained elusive up to date. Here we comparatively study cohorts of patients with Major and Non-Major Burns as well as healthy donors. MICB and ULBP1 are stress ligands of NKG2D that can be induced by heat stress. Remarkably, serum concentration levels of MICB and ULBP1 are increased by 3-fold and 20-fold, respectively, already within 24h post major thermal injury, and are maintained high for 28 days. In contrast, milder thermal injuries do not similarly enhance the serum levels of MICB and ULBP1. This kinetics coincides with a significant downregulation of NKG2D expression among peripheral blood NK cells. Downregulation of NKG2D by high concentration of soluble MICB occurs in cancer patients and during normal pregnancy due to over production by cancer cells or extravillous trophoblasts, respectively, as an active immune-evasion mechanism. In burn patients this seems an incidental outcome of extensive thermal injury, leading to reduced NKG2D expression. Enhanced susceptibility of these patients to opportunistic viral infections, particularly herpes viruses, could be explained by the reduced NKG2D expression. Further studies are warranted for translation into innovative diagnostic or therapeutic technologies.

Phenotype and functions of natural killer cells in critically-ill septic patients

Rationale

Natural killer cells, as a major source of interferon-γ, contribute to the amplification of the inflammatory response as well as to mortality during severe sepsis in animal models.

Objective

We studied the phenotype and functions of circulating NK cells in critically-ill septic patients.

Methods

Blood samples were taken <48 hours after admission from 42 ICU patients with severe sepsis (n = 15) or septic shock (n = 14) (Sepsis group), non-septic SIRS (n = 13) (SIRS group), as well as 21 healthy controls. The immuno-phenotype and functions of NK cells were studied by flow cytometry.

Results

The absolute number of peripheral blood CD3–CD56⁺ NK cells was similarly reduced in all groups of ICU patients, but with a normal percentage of NK cells. When NK cell cytotoxicity was evaluated with degranulation assays (CD107 expression), no difference was observed between Sepsis patients and healthy controls. Under antibody-dependent cell cytotoxicity (ADCC) conditions, SIRS patients exhibited increased CD107 surface expression on NK cells (62.9[61.3–70]%) compared to healthy controls (43.5[32.1–53.1]%) or Sepsis patients (49.2[37.3–62.9]%) (p = 0.002). Compared to healthy (10.2[6.3–13.1]%), reduced interferon-γ production by NK cells (K562 stimulation) was observed in Sepsis group (6.2[2.2–9.9]%, p<0.01), and especially in patients with septic shock. Conversely, SIRS patients exhibited increased interferon-γ production (42.9[30.1–54.7]%) compared to Sepsis patients (18.4[11.7–35.7]%, p<0.01) or healthy controls (26.8[19.3–44.9]%, p = 0.09) in ADCC condition.

Conclusions

Extensive monitoring of the NK-cell phenotype and function in critically-ill septic patients revealed early decreased NK-cell function with impaired interferon-γ production. These results may aid future NK-based immuno-interventions.

Trial Registration

NTC00699868.

Immunologic responses to critical injury and sepsis

Almost 2 million patients are admitted to hospitals in the United States each year for treatment of traumatic injuries, and these patients are at increased risk of late infections and complications of systemic inflammation as a result of injury. Host response to injury involves a general activation of multiple systems in defending the organism from hemorrhagic or infectious death. Clinicians have the capability to support the critically injured through their traumatic insult with surgery and improved critical care, but the inflammatory response generated by such injuries creates new challenges in the management of these patients. It has long been known that local tissue injury induces systemic changes in the traumatized patient that are often maladaptive. This article reviews the effects of injury on the function of immune system cells and highlights some of the clinical sequelae of this deranged inflammatory-immune interaction.

Immunological control of methicillin-resistant Staphylococcus aureus (MRSA) infection in an immunodeficient murine model of thermal injuries

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is a major cause of sepsis in patients who are immunosuppressed by their burns. In this study, an immunological regulation of MRSA infection was attempted in a mouse model of thermal injury. SCIDbg mice were resistant to MRSA infection, while SCIDbgMN mice (SCIDbg mice depleted of neutrophils and macrophages (Mphi)) were susceptible to the same infection. Also, thermally injured SCIDbg mice were shown to be susceptible to MRSA infection. On the other hand, the resistance of SCIDbgMN mice to the infection was completely recovered after an inoculation with Mphi from normal mice. However, anti-MRSA resistance was not shown in SCIDbgMN mice inoculated with Mphi from thermally injured mice. Mphi from MRSA-infected thermally injured mice were identified as alternatively activated Mphi, and Mphi from MRSA-infected unburned mice were characterized as classically activated Mphi. Mphi from thermally injured SCIDbg mice previously treated with 2-carboxyethylgermanium sesquioxide (Ge-132) protected SCIDbgMN mice against MRSA infection. Ge-132 has been described as an inhibitor of alternatively activated Mphi generation. These results suggest that MRSA infection in thermally injured patients is controlled immunologically through the induction of anti-MRSA effector cells and elimination of burn-associated alternatively activated Mphi, which are cells that inhibit the generation of classically activated Mphi.

Effect of IL‐12 and soluble IL‐4 receptor on the herpesvirus infection in human SCID chimeras whose Th2 cells predominate

Th2 cytokines, commonly detected in burn patients, have been shown as inhibitors for the generation of Th1 cells that are essential for the host's resistance against herpes simplex virus type 1 (HSV-1) infection. In this study, the possibility of immunological treatment through the regulation of Th1/Th2 responses was examined in two kinds of human severe combined immunodeficiency (SCID) chimera models reflecting human immune functions. SCID mice injected with a mixture of PBMC from a healthy donor and Th2 cells experimentally generated from the same healthy PBMC (Th2 SCID chimeras) were more susceptible to HSV-1 infection when compared with SCID mice injected with healthy donor PBMC (healthy SCID chimeras). When Th2 SCID chimeras were individually treated with human IL-12 (hIL-12) or human soluble IL-4 receptor (hsIL-4R), hIFN-gamma was not produced in their sera after antihuman CD3 mAb stimulation. However, hIFN-gamma production in sera of Th2 SCID chimeras treated with the combination therapy of hIL-12 and hsIL-4R was recovered at levels observed in healthy SCID chimeras. When Th2 SCID chimeras infected with HSV-1 were treated with saline, hIL-12, hsIL-4R or a combination of hIL-12 and hsIL-4R, 13%, 13%, 25% or 100% of them survived, respectively. Also, Th1 responses (hIFN-gamma production) were demonstrated in Th2 SCID chimeras that became resistant against HSV-1 infection after the combination treatment. These results suggest that individuals whose Th2 cells predominated may be immunologically controlled by the combination treatment between a Th1 response inducer and a Th2 response inhibitor.

The role of the sympathetic nervous system in moxibustion-induced immunomodulation in rats

The effects of chemical sympathectomy on moxibustion-induced changes in splenic natural killer (NK) cell cytotoxicity, T and B cell proliferation were studied. Direct moxibustion was applied to the unilateral Zusanli region. NK cell cytotoxicity was suppressed by moxibustion in both vehicle-treated rats and sympathectomized rats. T cell proliferation was not affected by moxibustion. B cell proliferation showed no significant change in vehicle-treated rats, but an increase was seen in sympathectomized rats treated with moxibustion. Sympathectomy alone induced an augmentation of NK cell cytotoxicity and a suppression of T cell proliferation. These results suggest that the sympathetic nervous system (SNS) has no significant role in the mechanism of moxibustion-induced immunomodulation.

The role of interleukin 6 in interferon-gamma production in thermally injured mice

Following traumatic injury, patients suffer from compromised immunity increasing their susceptibility to infection. Previous studies from this laboratory demonstrated that female BALB/c mice subjected to a 15% total body surface area (TBSA) scald injury exhibit a decrease in cell-mediated immunity 10 days post-burn. Studies described herein revealed that concanavalin A (Con A; 2 microg/ml)-stimulated splenocytes from sham treated animals produced 3557+/-853 pg/ml of IFN-gamma while splenocytes from burn injured animals released two-fold more cytokine (P<0.05). To determine whether leukocyte production of IFN-gamma was under the influence of macrophages, splenic macrophage supernatants generated from burned animals were incubated with splenic lymphocytes from sham and burn animals. The amount of IFN-gamma released by lymphocytes from sham animals increased when cultured with macrophages from burned mice (P<0.05). This suggests that the increase in IFN-gamma production by unfractionated splenocytes in burned mice relative to sham treated animals is macrophage-dependent. Macrophage supernatants from burned mice released twice as much IL-6 as supernatants from sham animals (P<0.05), and when IL-6 was blocked in vivo, the amount of IFN-gamma production in burned mice decreased to sham levels (P<0.05). Thus, IL-6 mediates IFN-gamma production following burn.

Thermal injury

Intensive care management of severely burned patients demands expertise in several areas. These include airway management, fluid resuscitation, support of the hypermetabolic response, infection control, and treatment of smoke inhalation injury. Surgical management of the burn wound, plastic reconstruction, and long-term rehabilitation are also essential aspects of modern burn care.

Inhibiteur de rejet de greffe alpha2-macroglobulin in burn injury: a suppressive activity on complement

A subform of alpha2-macroglobulin, (inhibiteur de rejet de greffe (IRG), present at a low rate in healthy rat, increased with rate-related suppressive activity on complement during inflammatory processes. In human serum, a molecule with such properties was described. Serum and blister IRG from burn patients belonging to a selected population was purified under gentle conditions. Serum IRG increased quickly within the first day after hospitalization and continued to increase until day 6. Although absent in whole serum, the rate-related activity of IRG varied according to the surface area and the degree of burns. A rate-related activity was also revealed in whole blister fluid and in purified blister IRG. We report a new site and a new suppressive activity of IRG in its native form from serum and blister fluid during inflammatory processes of burned patients. The suppressive activity of IRG on complement is discussed, and it appears to play a role in the development of inflammatory processes.

The regulation of burn-associated infections with herpes simplex virus type 1 or Candida albicans by a non-toxic aconitine-hydrolysate, benzoylmesaconine. Part 1: Antiviral and anti-fungal activities in thermally injured mice

As compared with normal unburned mice, thermally injured mice have been shown to be 50-100 times more susceptible to HSV type 1 (HSV-1) or Candida albicans infection. Benzoylmesaconine (BEN) improved the resistance of thermally injured mice against infection with HSV-1 or C. albicans to the level observed in normal mice. Mortality rates of normal mice exposed to lethal amounts of these pathogens were not affected by the BEN treatment, while significant survival effects were produced in these mice after treatment with acyclovir (against HSV-1) or amphotericin B (against C. albicans). Benzoylmesaconine did not inhibit the growth of these pathogens in vitro and did not directly reduce the viability of the pathogens. However, burned mice inoculated with CD4+ T cells from BEN-treated mice resisted infections from these pathogens. These results suggested that, through the generation of CD4+ T cells, BEN recovered the impaired resistance of thermally injured mice to infection by HSV-1 or C. albicans.

Early but not late burn wound excision partially restores viral-specific T lymphocyte cytotoxicity

OBJECTIVE

Early burn wound excision restores immunocompetence and improves patient survival, but the exact mechanisms have not yet been defined. Burn injury impairs cytotoxic T lymphocyte (CTL) activity as a function of burn size, increasing the risk of infection. The purpose of this study was to determine if early wound excision improved viral-specific CTL function.

METHODS

Anesthetized C57BL/6 mice (n = 20) received 0%, 20%, or 40% total body surface area full-thickness contact burns and were inoculated 3 days later with intraperitoneal lymphocytic choriomeningitis virus. Eight days after infection, or 11 days after burn, CTL effectors (E) were harvested and tested against infected, radiolabeled L-Dh targets (T) in a 51Cr-release assay, at varied E:T ratios. Dilution curves of CTL activity were compared by analysis of variance. In the second experiment, mice (n = 18) underwent a 30% burn that was totally excised and grafted on postburn days (PBDs) 0, 3, and 7. Control groups included sham burn and no excision of a 30% burn. In the third experiment, mice (n = 22) received a 30% burn that was partially, completely, or not excised on PBD 3. Control groups included sham burn with and without excision. All groups were infected with intraperitoneal lymphocytic choriomeningitis virus on PBD 3. Viral-specific CTL activity was determined on PBD 11.

RESULTS

Both 20% and 40% burn injury impaired viral-specific CTL function. Wound excision on PBDs 0 and 3, but not on PBD 7, partially restored CTL function. Total excision of the 30% burn improved CTL activity to a greater extent than did partial excision.

CONCLUSION

Burn injury inhibits viral-specific CTL activity. Early, complete wound excision augments CTL function. Improved CTL activity after burn may reduce the risk of infection, providing an immunologic rationale for expeditious wound excision.

Rationale, design and performance of a clinical trial to investigate interferon-gamma (Imukin) in the prophylactic treatment of severe burns-related infections

Recent advances in resuscitation therapy have increased the survival rate of patients with severe burns in the burn shock phase. Infectious complications represent the major cause of death in patients with extensive burns, however, in spite of the application of early and aggressive interventions. Extensive burn injury causes profound alterations in various essential elements of the normal host immune response and the main aim of treatment after resuscitation is to maintain or even improve host resistance. The positive anti-infective effects of interferon (IFN)-gamma observed in animal models and in clinical studies, for example in chronic granulomatous disease, provided the rationale for a study to investigate its use in patients with severe burns. A study was therefore designed to determine the efficacy and tolerance of IFN-gamma in preventing death related to infection in patients with severe burn injury who are at risk of infection. In order to avoid unnecessary risk for patients and reduce the cost, a sequential design was chosen. The primary end-point was reviewed in a group sequential manner after every 60 patients through an independent monitoring board. The study was a randomised, double-blind, Phase III multi-centre trial, conducted at 23 European Burn Centres. An interval censored survival time approach was taken, using information collected at days 8, 15, 30, 60, and 90. The trial is still blinded, but the rationale for conducting the study and its design are discussed.

Glycyrrhizin (20 beta-carboxy-11-oxo-30-norolean-12-en-3 beta-yl-2-O-beta-D-glucopyranuronosyl-alpha-D-glucopyranosiduronic acid) improves the resistance of thermally injured mice to opportunistic infection of herpes simplex virus type 1

The effect of glycyrrhizin (GR) on the resistance of thermally injured mice to opportunistic herpes simplex virus type 1 (HSV) infection was investigated. We have previously reported that the susceptibility of thermally injured mice or normal mice inoculated with T6S cells (a clone of burn-associated CD8+ CD11b+ TCR gamma/delta + type-2 suppressor T cells), to HSV infection was about 100 times greater than it was in normal mice. When thermally injured mice were treated i.p. with a 10 mg/kg dose of GR 2 and 4 days after infection of HSV, the resistance of these mice to HSV was improved to levels observed in normal mice. The adoptive transfer of splenic mononuclear cells (MNC) from normal mice treated with GR (GR-MNC) to thermally injured mice (recipients) resulted in the improved resistance of recipients to HSV infection. Normal mice inoculated with T6S cells and exposed to HSV had an 80% mortality rate, when given GR-MNC they had a 95% survival rate. The suppressor cell activity of T6S cells was clearly counteracted by GR-MNC in vitro in a mixed lymphocyte-tumor cell reaction. The type of cells responsible for anti-suppressor cells in GR-MNC was shown to be a CD4+ CD28+ TCR alpha/beta + Vicia villosa lectin-adherent T cell. These results suggest that GR may reverse the increased susceptibility of thermally injured mice to HSV infection through the induction of CD4+ contrasuppressor T cells.

Effects of a traditional Chinese herbal medicine, Kanzo-bushi-to, on the resistance of thermally injured mice infected with herpes simplex virus type 1

The protective effect of Kanzo-bushi-to (TJS-038) was investigated on the opportunistic infection of herpes simplex virus type 1 (HSV) in thermally injured mice (TI-Mice). We have previously reported that TI-Mice were approximately 100 times more susceptible to HSV infection than normal mice (N-Mice) and that CD8+ suppressor T (ST)-cells induced by burn injury were involved in causing this increased susceptibility of TI-Mice. Increased susceptibility of TI-Mice to the infection was reversed to the levels observed in N-Mice when TI-Mice were treated intraperitoneally with TJS-038 at a dose of 5 mg/kg 1 and 4 days after thermal injury. The activity of ST-cells was greatly decreased in TI-Mice treated with TJS-038. The generation of Vicia villosa lectin-adherent CD4+ CD28+ TCR-alpha/beta+ contrasuppressor T (Contra-ST)-cells associated with the appearance of ST-cells was expanded and occurred earlier in spleens of TJS-038-treated TI-Mice as compared with that of untreated TI-Mice. The improved resistance of TJS-038-treated TI-Mice to the infection was transferred to untreated TI-Mice by adoptive transfer of Contra-ST-cells prepared from TJS-038-treated TI-Mice. These results suggest that TJS-038 may restore the resistance of TI-Mice to the HSV infection through the expanded generation of Contra-ST-cells.

Reduction in circulating levels of CD4-positive lymphocytes in acute pancreatitis: relationship to endotoxin, interleukin 6 and disease severity

The proportion of peripheral blood mononuclear cells expressing the T helper cell phenotype and levels of antiendotoxin core antibody, interleukin (IL) 6 and C-reactive protein (CRP) were determined within 48 h of admission in a group of 29 patients with acute pancreatitis (16 mild, 13 severe attacks). There was a significant decrease in the proportion of T helper cells (12.2 versus 34.9 per cent, P < 0.01) and significant increases in levels of IL-6 (69.5 versus < 10 pg/ml, P < 0.01) and CRP (119 versus 30.5 mg/l, P < 0.01) in severe compared with mild attacks. During the convalescent stage at 3 months after admission, severe attacks were characterized by a significant increase in the proportion of T helper cells compared with the acute period (22.4 versus 10.6 per cent, P < 0.01). A persistently low proportion of T helper cells was associated with residual pancreatic necrosis. The presence of circulating endotoxin was demonstrated in two mild and two severe attacks using the Limulus amoebocyte lysate assay, and abnormal levels of antiendotoxin core antibodies were found in 70 and 92 per cent of mild and severe attacks respectively. There was a strong inverse correlation between levels of CRP and the proportion of T helper cells in severe disease (r = -0.76, P = 0.004). Translocation of endotoxin from the gastrointestinal tract may partly explain the abnormal levels of T helper cells, IL-6 and CRP.

Inhibition of burn-associated suppressor cell generation by glycyrrhizin through the induction of contrasuppressor T cells

The inhibitory effect of glycyrrhizin (GR), an anti-inflammatory Chinese herbal drug extracted from licorice roots, on the generation of suppressor T cells in thermally injured mice (TI-mice) was investigated. The burn-associated suppressor T cell (BTs cell) activity was demonstrated in splenic mononuclear cells (SMNC) from mice 2 to 8 days after thermal injury when suppressor cell activity was assayed in a one-way mixed lymphocyte reaction. However, when TI-mice were treated with GR, SMNC harvested 6 days after thermal injury showed no suppressor cell activity. This activity of GR demonstrated a dose-response effect, with a dose of 10 mg/kg exhibiting peak levels of the activity. Since GR had no direct inactivating activities against BTs cells in vitro, the inhibitory effect of SMNC, derived from TI-mice treated with GR, on the activity of BTs cells was examined in the same mixed lymphocyte reaction system, and the results showed that the SMNC from GR-treated mice 6 days after thermal injury counteracted the activity of BTs cells. The type of cell responsible for this inhibition of BTs cell activities was a CD3+, L3T4+, Vicia villosa lectin-adherent T cell with the same phenotypic properties previously exhibited by contrasuppressor cells. These results suggest that GR may regulate the generation of BTs cells through the induction of contrasuppressor cells. Since there are many reports describing septic infections due to the appearance of BTs cells in postburn patients, it may be possible to apply GR or blood preparations containing contrasuppressor cell populations induced by GR in healthy volunteers into immunosuppressed burn patients to avoid infections.

Temporal analysis of human leucocyte surface antigen expression and neutrophil respiratory burst activity after thermal injury

Sepsis, the major cause of morbidity and mortality after burn injury, is related to multiple immune derangements. Using monoclonal antibodies and two-colour flow cytometry to identify surface antigens, peripheral blood mononuclear cell (PBMC) populations were analysed and correlated with lymphocyte proliferation assays for 21 days postinjury. In addition, in vitro expression of activation antigens by mitogen-stimulated PBMCs was analysed during the time period. Twenty-nine burn patients were studied, with burn injuries ranging from 19 to 97 per cent TBSA; PBMCs from human volunteers were used for control cells. Patients received aggressive enteral nutritional support starting day 1 postburn and underwent early excision and grafting of wounds; no patients developed sepsis during the study period. The most consistent changes in PBMCs after thermal injury were decreased percentages of total T cells (CD3+), T helper/inducer cells (CD4+), and T suppressor/cytotoxic cells (CD8+); the percentages of natural killer (CD16+) cells were not altered. Expression of surface 'activation' antigens on CD4+ and CD8+ cells (HLA-DR, interleukin-2 receptor and transferrin receptor) after mitogen stimulation was significantly depressed as early as 1 day postburn. An early monocytosis was seen on day 1 postburn, but decreases were found on days 4 and 7. Monocyte expression of HLA-DR antigen was suppressed throughout the study. Lymphocyte proliferation after mitogen stimulation and the responses of lymphocytes in mixed lymphocyte culture were suppressed postburn. Neutrophil respiratory burst responses were supranormal on days 1 and 7 postburn, but the differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Early burn wound excision significantly reduces blood loss

The hypothesis that near-total early excision of large burns in children can be performed safely with a reduction in blood loss was tested. Of 1662 acutely burned patients admitted to this institution between 1982 and 1989, 594 underwent near-total excision of cutaneous flame or scald burn injuries in a single procedure. Operations took less than 3 hours and there were no operative deaths. Blood losses in burns of more than 30% total body surface area (TBSA) were significantly less at 0.40 +/- 0.06 mL/cm2 and 0.49 +/- 0.49 mL/cm2 excised when surgery was performed within the first 24 hours or after the 16th day after burn, respectively, when compared to 0.75 +/- 0.02 mL/cm2 for those excised between 2 and 16 days after burn (p less than 0.05). Blood loss for burns of less than 30% TBSA was of 1.19 +/- 0.13 mL/cm2. Early excision did not increase mortality rate when compared to later excision times. We suggest that near-total excision of large burns within the first 24 hours reduces blood requirements and morbidity without adversely altering hemodynamic stability or increasing mortality risks.

Changes in serum level and affinity for concanavalin A of human alpha 1-proteinase inhibitor in severe burn patients: relationship to natural killer cell activity

In serum from five patients with severe burns, alpha 1-proteinase inhibitor (alpha 1-PI) was analyzed and then isolated by immunosorption chromatography. By Con A-Sepharose chromatography alpha 1-PI was separated into two types of fractions: the first containing the Con A-non-reactive isoforms and the second containing the Con A-reactive isoforms. The increase of alpha 1-PI serum level in burn patients is associated on the fifth day after the burn with a significant shift toward species enriched in bi-antennary oligosaccharides (Con A-reactive isoforms). This latter change passed very quickly and ten days after the burn, whereas the alpha 1-PI serum level was still high, the difference in proportions of Con A-reactive and non-reactive isoforms was not statistically significant. With respect to the difference in oligosaccharide structure, it appeared that the glycan moiety was involved in the inhibitory effect on natural killer cell activity. At the same concentration, purified alpha 1-PI and retained alpha 1-PI isoforms had an equal effect, whereas the non-retained alpha 1-PI isoforms were more efficient (P less than or equal to 0.01). Purified alpha 1-PI and its isoforms inhibited the natural killer cell activity in a dose-dependent manner.

Trauma peptide induction of lymphocyte changes predictive of sepsis

Post-trauma immunosuppression is characterized by T-cell subpopulation changes and the presence of a low molecular weight suppressive active peptide (SAP), which suppresses T-cell blastogenesis and neutrophil chemotaxis. This study evaluated post-trauma T-cell antigens and suppressive active peptide/T-cell interactions to determine if the suppressive active peptide concentrations predictive of sepsis can cause changes in antigen expression predictive of sepsis. Human lymphocyte markers and differentiation antigens were analyzed post-trauma using flow cytometry for markers predictive of sepsis. Changes induced by purified suppressive active peptide incubated with normal human lymphocytes were similarly analyzed by flow cytometry. SAP concentrations for incubation were chosen which correlated with concentrations in patients developing clinical sepsis. Significant T-cell changes in patients who developed sepsis include: decreased total T-cells, decreased helper cells, decreased natural killer cells, increased Ia expressing mononuclear cells, increased activated T-cells, (L22) and increased IL-2 expressing cells (TAC). Suppressive active peptide can activate T-cells and cause significant increased expression of IL-2 receptors and natural killer cells. Other T-cell changes following trauma predictive of sepsis seem to occur independent of in vitro incubation with suppressive active peptides. IL-2 expressing cells are known to be more readily suppressed by the suppressive peptide. Suppressive peptide activation and subsequent inhibition of T-cells suggests a potential way to explain suppressive peptide-induced immunosuppression following trauma.

Effect of immunoglobulin G therapy on serum antibody titers to cytomegalovirus in burn patients

We attempted to determine the incidence and significance of cytomegalovirus infection and the effect of immunoglobulin G infusions on specific cytomegalovirus titers in burn patients. On admission, 48 percent of a group of 120 patients (mean burn size 28.5 percent of the total body surface area) were seronegative, including 95 percent of all patients under 20 years of age. Subsequently, 4 of a subgroup of 26 patients (15 percent) had development of a primary infection, and 1 of these patients died from overwhelming bacterial infection. Immunoglobulin G infusion used in the prophylaxis of the septic complications achieved high titers of cytomegalovirus-specific immunoglobulin G, as well as the subsets immunoglobulin G1 and immunoglobulin G3 which are also active against cytomegalovirus.

Natural killer cell activity following thermal injury

The role of natural killer cell activity in immunosurveillance following thermal injury remains unknown. We utilize a chromium-51-release assay of K562 targets to monitor NK activity. NK activity of peripheral blood mononuclear cells of severely burned patients (BSA greater than 20%) was determined once a week until the convalescence period was completed. From the second week after thermal injury, impairment of NK activity was demonstrated, but the differences did not reach statistical significance. However, a correlation was found between decline of NK activity and incidences of septic complications. Surprisingly, no decline in NK activity was observed in the first week after thermal injury.

Peripheral blood lymphocytes from thermal injury patients are defective in their ability to generate lymphokine-activated killer (LAK) cell activity

We have previously shown that natural killer (NK) cell activity against K562 tumor cells is severely depressed in thermal injury patients. In this study we have investigated whether the low NK cell activity present in peripheral blood lymphocytes (PBL) from thermal injury patients could be enhanced by in vitro culture with interleukin 2 (IL2) and whether PBL obtained from these patients could generate lymphokine-activated killer (LAK) cell activity against NK insensitive tumor targets. NK cell activity in PBL obtained from 12 different patients was greatly enhanced against K562 tumor cells after in vitro culture with IL2 for 3 days. In contrast, PBL obtained from these patients and incubated with IL2 had little to no cytotoxic activity when measured against a number of NK-insensitive tumor targets. The failure of PBL obtained from thermal injury patients to generate LAK cell activity was observed regardless of the culture time or the amount of IL2 added to the cultures. PBL from thermal injury patients demonstrated reduced proliferative responses to IL2 and, more importantly, contained suppressor cells which could inhibit the generation of LAK cell activity of normal PBL obtained from control individuals. These results clearly show that in some thermal injury patients NK cell activity can be enhanced by IL2 but these patients are defective in their ability to generate LAK cell activity.

Kinetics of lymphoproliferative responses following scald injury in a rat burn model

Splenic lymphocytes from scalded and nonscalded rats were studied for their proliferative response to phytohemagglutinin, and to allogeneic cells in a one-way mixed lymphocyte culture (MLC). A significant suppression of the proliferation of lymphocytes in both these assays was observed as early as 4 days postinjury as measured by the [3H]thymidine uptake studies. The lymphocyte response to PHA returned to normal levels by Day 21 postinjury, whereas the MLC responses continued to be suppressed. The MLC responses between nonburned and burned animals could be restored by the addition of a lymphokine-rich culture supernatant obtained from concanavalin A-activated lymphocytes from normal nonburned rats, as well as by the addition of purified human interleukin 2 (IL-2) and rat interleukin 2. However, the addition of purified human interleukin 1 and human interferon gamma (Hu-IFN-gamma) did not bring about a significant change in the proliferation of burned rat spleen cells in MLC. Cells from burned rats were also tested for the development of suppressive activity by adding splenic lymphocytes from 2-week postburn rats to an ongoing one-way MLC. The addition of lymphocytes from burned rats resulted in significant suppression (81%) of MLC responses among normal nonburned rats. The data suggest that the development of suppressor cells following burn injury along with a defect in production and/or uptake of IL-2 may be partly responsible for immune suppression following burn injury. Since the proliferative response of lymphocytes from thermally injured rats is suppressed in a similar fashion as that found in thermally injured patients, the rat appears to be a good model for the study of kinetics of immune suppression following burn injury.

Suppression of natural killer-cell function in humans following thermal and traumatic injury

Depressed cell-mediated and humoral immune functions have been reported to occur following severe thermal and traumatic injury. In this study we have questioned whether another immune function, natural killing (NK), is also disturbed in these injured patients. Twenty-two thermally injured patients with burns ranging from 5 to 75% of the total body surface area and 15 traumatically injured patients with injury severity scores ranging from 9 to 56 were followed postinjury and compared to 29 age-matched controls. NK activity was measured as the percentage cytotoxicity in chromium-51 release assays with K562 target cells. The more severely burned patients had significantly depressed NK activity for the 40-day period following injury that remained reduced for the duration of the study. Patients with lesser burns had reduced NK-cell function for the initial 10-day period postburn that returned slowly to the normal range. Traumatically injured patients had depressed NK-cell function during the 3- to 6-day period postinjury. The percentage of cells bearing phenotypic markers for the groups in which NK cells are found was either normal or elevated in these patients. A correlation was found between NK activity and interleukin 2 generation by mononuclear cells from these patients. In order to investigate the mechanism of NK suppression in these patients, NK-cell function was studied following the infusion of cortisol, epinephrine, and glucagon into volunteer subjects in amounts known to reproduce serum levels seen following injury of moderate severity. NK-cell function was reduced an average of 66% following infusion, suggesting that the inhibition of NK-cell function seen in patients may be mediated by the stress response to injury.

Leukocytic functions in burn-injured patients

Anergy associated with an increase in suppressor helper T cell (Tc) ratio and a decrease in natural killer (NK) is one main cause of death following thermal injury (Tl). Recently, in vitro studies have shown that LTB4 can induce human Tc to exert suppressor cell activity, and incubation of lymphocytes with LTB4 for 24 hours significantly suppressed NK cell activity. Thus, we undertook an investigation of both AA metabolism and immunologic response in 20 patients who suffered 40-90% total body surface area (TBSA) burns. Cyclooxygenase (CO:RIA) and lipoxygenase (LO;HPLC det.) metabolites and superoxide (O2 X-) production were measured in stimulated polymorphonuclear cells (PMNL) (A 23187 +/- AA for icosanoid release; phorbol myristate acetate for O2 X-production). Lyso-paf-acether (P-LPA) was measured in plasma samples. Ca2+-dependent K+permeability in PMNL was measured by the cell K+ release induced by A 23187. Tc and Tc subsets were determined using monoclonal antibodies (OKT3+, OKT4+ and OKT8+). A biphasic sequential release of the different substances (leukocytic icosanoids and O2 X-) was monitored: increase (approximately 36-48 h after Tl) and decrease (greater than or equal to 72 h after Tl). The increase in AA stimulation was more transient than that of O2 X -. The decline in the release of AA metabolites and O2 X-production was associated with the anergic phase (decrease OKT4+/OKT8+ ratio) and with the clinical outcome of the patients. The decrease in LTB4 and other LO metabolites could explain the impairment of neutrophil chemotaxis. Ca2+-dependent K+ permeability increased early up to 2 or 3 times normal. In order to go further with the mechanism of inhibition of LTB4 and O X-release, the effect of Tl plasma was assayed on normal leukocytes: a 10 min incubation with such plasma was sufficient to abolish LTB4 secretion. A less important inhibition was observed with O2 X-release (-32%) and Ca2+-dependent K+ permeability (-30%). Plasma inhibition seems to be due to a thermolabile factor(s) [protein(s): "suppressive factor(s) of membrane activation "SFMA] which is (are) under active investigation using gel-filtration chromatography and fast protein liquid chromatography (FPLC). Among the SFMAs, certain acute phase proteins could play a key role: i.e., incubation (10 min) of normal PMNL with ceruloplasmin (1 mg/ml) abolished LO products and O X 2-release.